feat: #78 Excalidraw finitions + #67 push + #68 health-detailed + #77 desktop jumplist

#78 Excalidraw — finitions B5/C8/F2/F3
- backend/indexer.py: port Python pur de lz-string decompressFromBase64 (bitsPerChar=6, resetValue=32) validé contre 4 fixtures JS truth (texte accentué, edge cases) — remplace le stub base64 non-fonctionnel
- B5 indexation: .excalidraw.md (format plugin Obsidian) maintenant décompressé côté Python → texte indexé pour recherche TF-IDF
- 7 nouveaux tests B5 dans tests/test_excalidraw.py (13/13 total)
- F2: excalidraw-viewer.test.mjs enregistré dans CI (lint job)
- F3: tests/e2e/excalidraw.spec.js (9 specs — ouverture .excalidraw/.excalidraw.md, création via modale/menu contextuel, toolbar, thème, pop-out, recherche)
- Fixtures test_vault/diagram.excalidraw + diagram.excalidraw.md

#67 Push notifications (Web Push API + VAPID)
- backend/push.py: router + VAPID keys + send_push_notification (pywebpush>=2.3.0)
- frontend/js/push.js: subscription UI + service worker integration
- tests/test_push.py: 10 tests (subscribe/list/unsubscribe/vapid key)
- requirements.txt + sw.js + locales push strings

#68 Health check enrichi
- backend/main.py: GET /api/health/detailed (admin) — memory/cpu/disk/backups/index/SSE connections
- backend/indexer.py: _last_full_index_ts tracking
- tests/conftest.py: admin_client fixture
- tests/test_api_main.py: 3 nouveaux tests health detailed

#77 Desktop jumplist
- desktop/src/jumplist.rs: Windows jumplist integration
- Cargo.toml/lock + capabilities + main.rs
- frontend/js/desktop.js: Tauri bridge (isTauriEnv, invoke, getSystemTheme, syncSystemTheme, shouldShowWizard, crash banner)
- tests/frontend/desktop.test.mjs: 21 tests JSDOM (détection, invoke degradation, theme gating, wizard, crash banner)
- tests/frontend/unit.test.mjs: desktop.js whitelisted (standalone global reader)

# Frontend & CI
- frontend/sw.js: réécriture complète (precache + push event handlers + offline)
- frontend/index.html: section push dans settings + about repositionné
- frontend/js/app.js: initDesktopIntegration + initPush
- CI .gitea/workflows/ci.yml: excalidraw-viewer.test.mjs ajouté au lint job

All checks: ruff clean, 552 backend tests pass, 9 frontend unit, 5 excalidraw-viewer, 21 desktop, 9 pane-manager, validate-imports 33 modules.

frontend/js/ui.js

@@ -755,10 +755,10 @@ const FileOperations = {
     });
   },
 
-  showCreateFileModal(vault, parentPath) {
-    const overlay = this._createModalOverlay();
-    const modal = document.createElement('div');
-    modal.className = 'obsigate-modal';
+  showCreateFileModal(vault, parentPath, preselectExt = null) {
+      const overlay = this._createModalOverlay();
+      const modal = document.createElement('div');
+      modal.className = 'obsigate-modal';
     modal.innerHTML = `
       <div class="obsigate-modal-header">
         <h3 class="obsigate-modal-title">${t('modal.create_file')}</h3>
@@ -804,6 +804,10 @@ const FileOperations = {
     
     input.focus();
     
+    if (preselectExt && [...extSelect.options].some(o => o.value === preselectExt)) {
+      extSelect.value = preselectExt;
+    }
+    
     const validateName = (name) => {
       if (!name.trim()) return 'Le nom ne peut pas être vide';
       if (/[/\\:*?"<>|]/.test(name)) return 'Caractères interdits: / \\ : * ? " < > |';
@@ -1695,6 +1699,7 @@ export const ContextMenuManager = {
     } else if (type === 'directory') {
       this._addItem('folder-plus', 'Nouveau sous-dossier', () => this._createDirectory(), isReadonly);
       this._addItem('file-plus', 'Nouveau fichier ici', () => this._createFile(), isReadonly);
+      this._addItem('pen-tool', 'Nouveau diagramme Excalidraw', () => this._createExcalidraw(), isReadonly);
       this._addSeparator();
       this._addItem('bookmark-plus', 'Ajouter aux recherches sauvegardees', () => this._saveDirectorySearch(), false);
       this._addSeparator();
@@ -1775,6 +1780,10 @@ export const ContextMenuManager = {
     FileOperations.showCreateFileModal(this._targetVault, this._targetPath);
   },
 
+  _createExcalidraw() {
+    FileOperations.showCreateFileModal(this._targetVault, this._targetPath, '.excalidraw');
+  },
+
   _renameItem() {
     FileOperations.startInlineRename(this._targetVault, this._targetPath, this._targetType);
   },